Abstract
BackgroundThe Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian?) of Utah has yielded a rich dinosaur fauna, including the basal therizinosauroid theropod Falcarius utahensis at its base. Recent excavation uncovered a new possible therizinosauroid taxon from a higher stratigraphic level in the Cedar Mountain Formation than F. utahensis.Methodology/Principal FindingsHere we describe a fragmentary skeleton of the new theropod and perform a phylogenetic analysis to determine its phylogenetic position. The skeleton includes fragments of vertebrae, a scapula, forelimb and hindlimb bones, and an ischium. It also includes several well-preserved manual unguals. Manual and pedal morphology show that the specimen is distinct from other theropods from the Cedar Mountain Formation and from previously described therizinosauroids. It is here named as the holotype of a new genus and species, Martharaptor greenriverensis. Phylogenetic analysis places M. greenriverensis within Therizinosauroidea as the sister taxon to Alxasaurus + Therizinosauridae, although support for this placement is weak.Conclusions/SignificanceThe new specimen adds to the known dinosaurian fauna of the Yellow Cat Member of the Cedar Mountain Formation. If the phylogenetic placement is correct, it also adds to the known diversity of Therizinosauroidea.
Highlights
The Cedar Mountain Formation (Lower Cretaceous) of Utah, USA, preserves a rich theropod paleofauna
Nomenclatural Acts The electronic version of this document does not represent a published work according to the International Code of Zoological Nomenclature (ICZN), and the nomenclatural acts contained in the electronic version are not available under that Code from the electronic edition
A gravelly, calcareous sandstone often hosting a stromatolitic layer at its top that divides the Yellow Cat Member into an upper and lower sequence [34,35] has been informally designated the caprock in this area
Summary
The Cedar Mountain Formation (Lower Cretaceous) of Utah, USA, preserves a rich theropod paleofauna. The paleofauna of the lower sequence of the Yellow Cat Member includes the basal therizinosauroid Falcarius utahensis [2,3,4], the troodontid Geminiraptor suarezarum [5], an unnamed velociraptorine dromaeosaurid [6], and the dromaeosaurine dromaeosaurid Yurgovuchia doellingi [6]. We describe a new theropod specimen from the upper Yellow Cat Member. The Yellow Cat Member of the Cedar Mountain Formation (Early Cretaceous, Barremian?) of Utah has yielded a rich dinosaur fauna, including the basal therizinosauroid theropod Falcarius utahensis at its base. Recent excavation uncovered a new possible therizinosauroid taxon from a higher stratigraphic level in the Cedar Mountain Formation than F. utahensis
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